Producer Bernie Brillstein was initially uninterested in seeing Paul Fusco's puppet audition, having worked with Jim Henson for years and considering him the best puppeteer in the business, but Fusco's brief performance as ALF won him over.

While ALF was mainly performed as a puppet by Paul Fusco, full-body shots of the character walking or running were played by 2 feet 9 inches (84 cm) actor Michu Meszaros wearing an ALF costume, though he was uncredited for the role.

The set was built on a raised platform with numerous trap doors so ALF could appear anywhere, with Fusco operating the puppet from underneath through deep holes in the floor that had to be reset multiple times, sometimes mid-scene.

Operating ALF required a team: Paul Fusco controlled the mouth and right arm, puppeteer Lisa Buckley (who later worked on Sesame Street) controlled the left arm from below, and Bob Fappiano remotely controlled the facial and ear movements, a process so complex that a 30-minute episode could take 20 to 25 hours to shoot.

Because the puppeteering process led to numerous mistakes and retakes, it was impossible to film ALF in front of a live studio audience, so a laugh track was added in post-production.

To spare wear and tear on the main ALF puppet, performers rehearsed with a crude early version nicknamed 'RALF' (Rehearsal Alien Life Form), and Fusco, who disliked rehearsing, often substituted his hand or RALF for the real puppet during run-throughs.

Cast members later described a tense and difficult set; Max Wright admitted he despised working with the demanding puppet and was eager for the show to end, and comedian Artie Lange recounted a time Wright became so frustrated he physically attacked the ALF puppet, requiring producers to pull him off.

Anne Schedeen said the final night of taping was so charged that Max Wright did one take, grabbed his bags from his dressing room, and left without saying goodbye to anyone.

Fusco was extremely secretive about the ALF puppet's production, insisting during filming that the puppet not be treated as anything other than a real alien, and cautioning everyone involved not to reveal production secrets.

After NBC reported that a child had placed a cat in a microwave after watching the show, jokes about ALF eating cats became a censorship issue, and network concerns about ALF being a bad role model led to the discontinuation of scenes showing him drinking beer.

For the episode 'Try to Remember,' NBC forced a re-edit after a child reportedly tried to recreate ALF's dangerous stunt of putting an electric mixer in a bathtub; the scene was changed to a simple slip in the shower for all future broadcasts.

Blooper footage that surfaced in 2010 showed ALF delivering racial and sexual jokes; producer Steve Lamar explained the footage was actually ALF mocking a contemporary episode of L.A. Law about Tourette syndrome, from an era less concerned with political correctness.

The German actor who dubbed ALF's voice, Tommi Piper, was popular enough that he recorded two albums and four singles in character as ALF between 1988 and 1991.